He identified six observations as a result of climate change, three of which with a high level of certainty would continue to happen. These were: carbon dioxide (CO2) rising; global warming and the increase in sea level.

“We are certain that the CO2 concentration is rising because of what we are doing as the human race. We are also certain that the world is warming,” he said.

“We are confident that these things are linked. It’s a no brainer that a warmer world means rising sea levels. These are the top three things that will continue to happen.”

However, Betts was concerned with the remaining three predictions due to a lack of detail about how these would occur in the future. These were: heavier rains; milder, wetter winters and hotter, drier summers.

Without policies on reducing greenhouse emissions, he warned the world would be 4°C above pre-industrial levels by the end of the century or “even a few decades before”. However, global average temperatures affect some areas faster than others, he warned. For instance, the polar regions could melt sooner.

On sea level increases, Betts presented two projections of the global average sea-level rise over the 21st century, and explained that under a high-risk scenario, without any efforts to cut emissions, the world could see a 0.5m to 1m sea-level rise by 2100.

Even with a lower emission scenario, which assumes rapid cuts under the agreements made at the Climate Change Conference in Paris, there could still be a rise of between 0.3-0.6m by the end of the century.

He added that a further rise could be possible if unexpected events happened such as parts of the Antarctic ice sheet collapsing.

In response to a question from the floor on the climate outlook beyond 2100, Betts said the most obvious forecast would be a further sea level rise but added: “Exactly how it will play out will depend on how the ice sheet responds”.